linux-kernel - Re: [PATCH] init: Introduce 'noinitramfs' kernel parameter

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Message-ID: <20140623000847.GA31648@khazad-dum.debian.net>
Date:	Sun, 22 Jun 2014 21:08:47 -0300
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Cc:	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Guido Martínez <guido@...guardiasur.com.ar>
Subject: Re: [PATCH] init: Introduce 'noinitramfs' kernel parameter

On Sun, 22 Jun 2014, Ezequiel Garcia wrote:
> On 22 Jun 11:53 AM, Henrique de Moraes Holschuh wrote:
> > On Sun, 22 Jun 2014, Ezequiel Garcia wrote:
> > > This commit adds a new kernel parameter to provide such option, following the
> > > naming of the current 'initrd' which serves a similar purpose, for an initial
> > > RAM disk.
> > 
> > How does it interact with the early initramfs?
> > 
> > Maybe we should have the options to ignore both, ignore just the early
> > initramfs (to skip microcode updates and ACPI table updates), and ignore
> > just the main initramfs?
> > 
> 
> I must admit I don't have much experience with any "earlier" initramfs.
> Maybe you can point me at some links about this?

Search for kernel code that includes the linux/earlycpio.h header file.  The
implementation is at lib/earlycpio.c.

I am sorry I don't have a better reference to point you to.

> Unless I'm missing something, this "early" initramfs is an userspace artifact
> in the construction of the initramfs, so the kernel has no way to distinguish

No, it is an uncompressed cpio archive which is parsed extremely early, for
critical system firmware (currently: processor microcode updates and ACPI
table overrides).

Documentation of its two current users is at:

Documentation/x86/early-microcode.txt
Documentation/acpi/initrd_table_override.txt

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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